Reef building at the nanoscale
Dr Mathieu Pernice first became interested in marine biology as a child, sailing with his family from Corsica to Sardinia in the summer. After completing his PhD on the bacterial symbiosis of deep sea nautiloids he came to Australia to study coral symbiosis, focussing on dinoflagellates, the photosynthesising single-celled algae that provide energy for the coral and aid in calcification. Today, as a Research Associate within the Plant Functional Biology and Climate Change Cluster (C3), he is applying innovative technology to better understand, and thereby safeguard, our coral reefs.
Dr Pernice and his colleagues, have recently published the results of research - funded by the Swiss National Science Foundation in collaboration with C3 - into the nutritional and energy exchanges between corals and two clades, or groupings, of Symbiodinium, the dinoflagellate symbionts most commonly associated with coral reefs
“There has been a lot of work on coral reefs and the fact that they are affected by global and local pressure and climate change ... and there is a fair bit of literature already showing that different symbiodinium can lead to different sensitivity to bleaching and thermal stress [in the coral]. However, the mechanisms underlying this differential sensitivity remain largely unexplored and it is still unclear if different Symbiodinium types possess different metabolic capabilities. The Symbiodinium we looked at in this paper are naturally associated with many reef building corals on the Great Barrier Reef– there were two groups, clade C and D, and the clade D is known as thermally tolerant. So the coral that host the symbiodinium D has more chance to resist coral bleaching and temperature increases,” Dr Pernice said.
Utilizing nanoSIMS (nanoscale secondary ion mass spectrometer) technology, Dr Pernice and his colleagues were able to visualise the exchanges between the coral host and symbiont.
“NanoSIMS is a very powerful tool for that because you don’t have to separate the coral from its symbiotic algae during sample preparation. You can image nutrient fixation and transfer at a very high resolution and you are able to say if one nutrient that was fixed by the dinoflagellate symbiont, was then transferred to the host. You are able to map basically the transfer of nutrients within the intact symbiosis,” Dr Pernice said.
Through the application of this technology the team discovered that although the less common clade D of Symbiodinium was less metabolically active than clade C, it conferred more resilience to bleaching and thermal stress to the coral.
“Which in a way makes sense and explains why most corals keeps this Symbiodinium C, which is more sensitive to thermal stress but at the same time more active so it gives them more energy and more nutrients,” Dr Pernice explains.
The next step for Dr Pernice and his colleagues is to examine the Symbiodinium’s metabolic response to thermal stress under predicted climate change scenarios.
Dr Pernice is also currently using molecular biology to develop sub-lethal markers of stress in coral and seagrass as a more effective tool for managing damaged areas. Rather than monthly assessments of coral or seagrass mortality, the aim is to provide managers with the ability to detect damage while there is still time to reverse it.
By Gemma Thompson
Mathieu Pernice, Simon R Dunn, Linda Tonk, Sophie Dove, Isabelle Domart‐Coulon, Peter Hoppe, Arno Schintlmeister, Michael Wagner, Anders Meibom, A nanoscale secondary ion mass spectrometry study of dinoflagellate functional diversity in reef-building corals, Environmental Microbiology, Article first published online: 30 JUN 2014, DOI: 10.1111/1462-2920.12518 (http://onlinelibrary.wiley.com/doi/10.1111/1462-2920.12518/abstract)